L-arginine is a conditional amino acid -- your body can't make it by itself, but you don't necessarily need it if you are in good health. That said, arginine supplementation has been explored as an aid to a variety of health conditions, including obesity. Although it doesn't work like a traditional diet pill, by increasing energy or blocking fat absorption, the evidence so far shows that it may be useful as an adjunct to a diet and exercise plan.
Initial Evidence
L-arginine has been used to prevent weight loss in people with wasting diseases. In fact, a 1994 study in the "British Journal of Surgery" found that jaundiced rats fed arginine supplements ate more food and lost less weight than the control group. This may sound like the opposite of a weight-loss drug -- after all, it increases the appetite -- but further research proved the mechanism to be just as effective at fat loss as at weight preservation.
Updated Findings
A 2006 study in the "Journal of Nutritional Biochemistry" found that arginine supplementation may help prevent or treat metabolic syndrome by reducing insulin resistance and enhancing blood flow to assist in the metabolism of stored fat. A 2009 Texas AgriLife study profiled in Science Daily expanded upon that research and showed that arginine supplementation substantially reduced fat gain in rats and increased muscle mass in pigs without affecting body weight. In other words, although the pigs didn't lose weight, they lost fat and gained muscle.
Application
The jury is still out on the weight-loss benefits of L-arginine -- there have not been enough human studies to ensure that the favorable effects translate across species lines. The evidence so far shows that it may be helpful if you are looking to lose fat and build muscle, but not if you are simply looking to lose weight. In the studies cited, the actual number on the scale did not fall as impressively as many dieters hope, but body composition improved and it appears that arginine may help some people respond better to a diet and exercise program.
Safety
L-arginine supplements are thought to be safe for most people short-term, although side effects like allergies, low blood pressure and digestive issues could result. You should not take L-arginine if you have asthma, herpes or have had a recent heart attack, or if you are taking blood pressure or nitrate drugs. Use with caution if you use Viagra or xylitol, and consult your doctor for the appropriate dose for you.
References
- MedlinePlus: L-Arginine
- "The British Journal of Surgery"; Modulation of Immune Function and Weight Loss by L-Arginine in Obstructive Jaundice in the Rat; Kennedy JA, et al.; August 1994
- "Journal of Nutritional Biochemistry"; Regulatory Role for the Arginine-Nitric Oxide Pathway in Metabolism of Energy Substrates; Jobgen WS, et al.; September 2006
- Science Daily; Arginine Discovery Could Help Fight Human Obesity; February 2009
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